The present invention relates to a method of controlling pitch on a gyroplane and a gyroplane which has been modified in accordance with the teachings of the method.
Gyroplanes are designed with a main keel tube or fuselage to which a mast is attached. On a pusher type gyroplane, the pilot is seated just in front of the mast and the engine is attached to the rear of the mast. On a tractor type gyroplane, the pilot is seated just behind or under the mast and the engine is attached to the front of the fuselage or keel tube. At the top of the mast is a rotor head, which is attached to the mast via a gimbaled head. The gimbaled head (universal joint) is controlled by the pilot via a series of push-tubes leading down to a vertical stick between the pilot""s legs. When the pilot pushes forward on the stick the rotor head tilts forward, and the reverse is true when the pilot pulls the stick to the rear. The pilot can also tilt the gimbaled rotor head to the left and to the right by moving the stick in the appropriate direction. The rotors on 90% of all gyroplanes are of the fixed pitch under-slung, teetering type. By tilting the rotor to the relative airflow the rotors will pick up enough speed to form a disc. This is essentially the wing that the gyroplane flies on. By tilting the disc forward the aircraft will descend, and by tilting the disc rearward the aircraft will ascend.
When the pilot moves the stick in the gyroplane he is tilting the entire disc in the direction that he wants to go. If you calculate the sq. ft of a 30 foot rotor disc. it comes out to 706 sq. feet. So the end result is that you have 706 sq. feet of elevator, and 706 sq. feet of aileron. Thus only a small control input is needed to do dramatic things. The pilot is flying the rotor disc, and the main body of the aircraft is like a pendulum below. So when the pilot moves the stick, there is a slight delay in actual movement of the body of the aircraft, relative to the disc. Thus in turbulent air the pilots concentration is a must. Also, the faster the forward speed of the gyroplane the smaller the control inputs are needed. This can lead to a pilot porpoising, which is a where the pilot gets out of phase with what the body of the aircraft is doing relative to the rotor disc. This can lead to the disc tilting to far forward to the relative airflow, causing fatal results. Air movement on a gyroplane rotor blade must be from the bottom out through the top. This air movement will keep the rotor in a steady state of auto-rotation. If the rotor disc is tilted too far forward to the relative wind, the airflow will reverse from the bottom through the top to the top out the bottom. All gyroplanes are more pitch sensitive than roll sensitive, this is to say that the aircraft pendulums more front to rear than side to side.
Previously, the way to counteract the pitch movement of the airframe was to put a horizontal stabilizer at the rear of the gyroplane close to the rudder. It was soon found that a very large span of horizontal tail surface was required to counter the pendulum movement of the airframe. Because the rotor tilts rearward, This limits the distance that the rudder and horizontal tail can be placed to the rear of the aircraft.
Furthermore, by adding the horizontal stabilizer to the keel, the gyroplane can be prevented from pitching up, however, it cannot climb as well. It then becomes very difficult to get climb or turn performance, more stick pressure is required to get the gyroplane to climb or turn. It was discovered that the horizontal tail, if not placed in the propeller slipstream did not actually stop the aircraft from pitching nose up or nose down in turbulent air, it sometimes made it more dramatic.
It was also found that by adding a horizontal tail, that the aircraft""s performance was dramatically reduced. When landing, the horizontal stabilizer makes the gyroplane float longer, cutting 30% off the performance of the gyroplane.
What is required is an alternative method of controlling pitch on a gyroplane.
According to one aspect of the present invention there is provided a method of controlling pitch on a gyroplane. A first step involves pivotally securing a wing to a mast supporting a rotor of the gyroplane. A second step involves providing a linkage between the wing and a rotor head. The linkage is secured to the rotor head with a universal joint connection so as not to restrict movement of the rotor head while maintaining a constant relationship between the wing and the rotor. A third step involves providing means for a pilot to lengthen and shorten the linkage while in flight in order to pivot the wing and thereby alter positioning of the wing relative to the rotor to help control the angle of the rotor relative to wind direction.
According to another aspect of the present invention there is provided a gyroplane which, includes an airframe and an upright mast extending from the airframe and supporting a gimballed rotor head on which a rotor is mounted. An engine is secured to the airframe and adapted to drive a propeller and momentarily drive rotor. A wing is pivotally secured to the mast. A linkage extends between the wing and the rotor head. The linkage is secured to the rotor head with a universal joint connection so as not to restrict movement of the rotor head while maintaining a constant relationship between the wing and the rotor. Means are provided for a pilot to lengthen and shorten the linkage while in flight, in order to pivot the wing and thereby alter positioning of the wing relative to the rotor to help control the angle of the rotor relative to wind direction.